Find what causes "permission denied: can not access account" error

Hi folks,

I run ZCS NE 6.0.12, with 6.0.9 ZCO clients.

I get the following reccurent error in my mailbox.log:

Code:

com.zimbra.common.service.ServiceException: permission denied: can not access account 7c6e9e52-f03d-4150-9d3d-250112477be0
ExceptionId:btpool0-63252://mail.oudart.local/service/soap/SyncRequest:1307438620512:32b2170f33343617
Code:service.PERM_DENIED
at com.zimbra.common.service.ServiceException.PERM_DENIED(ServiceException.java:278)
at com.zimbra.common.service.ServiceException.DEFEND_ACCOUNT_HARVEST(ServiceException.java:287)
at com.zimbra.soap.ZimbraSoapContext.<init>(ZimbraSoapContext.java:235)
at com.zimbra.soap.SoapEngine.dispatch(SoapEngine.java:203)
at com.zimbra.soap.SoapEngine.dispatch(SoapEngine.java:158)
at com.zimbra.soap.SoapServlet.doWork(SoapServlet.java:291)
at com.zimbra.soap.SoapServlet.doPost(SoapServlet.java:212)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
at com.zimbra.cs.servlet.ZimbraServlet.service(ZimbraServlet.java:181)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:814)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
at com.zimbra.cs.servlet.SetHeaderFilter.doFilter(SetHeaderFilter.java:79)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.servlet.UserAgentFilter.doFilter(UserAgentFilter.java:81)
at org.mortbay.servlet.GzipFilter.doFilter(GzipFilter.java:155)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:218)
at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:422)
at org.mortbay.jetty.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:230)
at org.mortbay.jetty.handler.HandlerCollection.handle(HandlerCollection.java:114)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at org.mortbay.jetty.handler.rewrite.RewriteHandler.handle(RewriteHandler.java:230)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at org.mortbay.jetty.handler.DebugHandler.handle(DebugHandler.java:77)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at org.mortbay.jetty.Server.handle(Server.java:326)
at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:543)
at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:946)
at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:756)
at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:218)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:405)
at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:410)
at org.mortbay.thread.BoundedThreadPool$PoolThread.run(BoundedThreadPool.java:451)

I think this is related to mounted delegations in a user's mailbox for users that doesn't exists anymore.
the question is how can I identify the source mailbox that is generating this error?